Do Field Walking Tests Produce Similar Cardiopulmonary Demands to an Incremental Treadmill Test in Obese Individuals With Treated OSA?

BACKGROUND: Cardiorespiratory fitness, assessed during cardiopulmonary exercise tests by peak oxygen uptake (<(V)over dot>O-2 pk), is an independent predictor of mortality in obesity. We investigated whether <(V)over dot>O-2 pk and systemic responses measured during field walking tests were similar to those measured during an incremental treadmill test (ITMT) in obese individuals with treated OSA. METHODS: Individuals with treated OSA and a BMI > 30 kg/m(2) were recruited. Participants completed an ITMT, two 6-min walk tests (6MWTs), and two incremental shuttle walk tests (ISWTs) on three separate days in a randomized order. Expired gas analysis was performed during all tests. RESULTS: The study was completed by 16 patients (nine men) (mean [SD] age, 58 [ 12] y; BMI, 36.1 [7.6] kg/m(2)). There was no difference (P = .27) in <(V)over dot>O-2 pk assessed by the ITMT and the ISWT (2,266 [478] and 2,017 [561] mL/min, respectively). The <(V)over dot>O-2 pk measured by the 6MWT (1,778 [360] mL/min) was lower than that measured by the ITMT (P < .01). The limits of agreement for <(V)over dot>O-2 pk between the ISWT and the ITM were +/- 730 mL/min. Cardiorespiratory responses during the ISWT and the ITMT reflected a graded response to a peak, whereas the 6MWT demonstrated a rapid rise to a plateau. CONCLUSIONS: The ISWT can be used instead of an ITMT and in preference to the 6MWT to assess cardiorespiratory fitness for a cohort of obese people with treated OSA. However, the imprecision of the agreement in <(V)over dot>O-2 pk between the ITMT and ISWT means they cannot be used interchangeably in an individual.